A wide variety of soil release agents for use in domestic and industrial fabric treatment processes such as laundering, fabric drying in hot air clothes dryers, and the like are known in the art. Various soil release agents have been commercialized and are currently used in detergent compositions and fabric softener/antistatic articles and compositions. Such soil release polymers typically comprise an oligomeric or polymeric ester “backbone”.
The term “soil-release” in accordance with the present invention refers to the ability of the fabric to be washed or otherwise treated to remove soil and/or oily materials that have come into contact with the fabric. The present invention does not wholly prevent the attachment of soils to the fabric, but hinders such attachment and improves the cleanability of the fabric.
Soil release polymers are generally very effective on polyester or other synthetic fabrics where the grease, oil or similar hydrophobic stains spread out and form an attached film and thereby are not easily removed in an aqueous laundering process. Many soil release polymers have a less dramatic effect on “blended” fabrics, namely fabrics that comprise a mixture of cotton and synthetic material, and have little or no effect on cotton articles. The reason for the affinity of many soil release agents for synthetic fabric is that the backbone of a polyester soil release polymer typically comprises a mixture of terephthalate residues and ethyleneoxy or propyleneoxy polymeric units; the same materials that comprise the polyester fibers of synthetic fabric. This similar structure of soil release agents and synthetic fabric produce an intrinsic affinity between these compounds.
Extensive research in this area has yielded significant improvements in the effectiveness of polyester soil release agents yielding materials with enhanced product performance and formulatability. Modifications of the polymer backbone as well as the selection of proper end-capping groups has produced a wide variety of polyester soil release polymers. For example, end-cap modifications, such as the use of sulfoaryl moieties and especially the low cost isethionate-derived end-capping units, have increased the range of solubility and adjunct ingredient compatibility of these polymers without sacrifice to soil release effectiveness. Many polyester soil release polymers can now be formulated into both liquid as well as solid (i.e., granular) detergents.
As in the case of polyester soil release agents, producing an oligomeric or polymeric material that mimics the structure of cotton has not resulted in a cotton soil release polymer. Although cotton and polyester fabric are both comprised of long chain polymeric materials, they are chemically very different. Cotton is comprised of cellulose fibers that consist of anhydroglucose units joined by 1-4 linkages. These glycosidic linkages characterize the cotton cellulose as a polysaccharide whereas polyester soil release polymers are generally a combination of terephthalate and ethylene/propylene oxide residues. These differences in composition account for the difference in the fabric properties of cotton versus polyester fabric. Cotton is hydrophilic relative to polyester. Polyester is hydrophobic and attracts oily or greasy dirt and can easily be “dry cleaned”. Importantly, the terephthalate and ethyleneoxy/propyleneoxy backbone of polyester fabric does not contain reactive sites, such as the hydroxyl moieties of cotton, which react with stains in different manner than synthetics. Many cotton stains become “fixed” and can only be resolved by bleaching the fabric.
Until now the development of an effective cotton soil release agent for use in a laundry detergent has been elusive. Attempts by others to apply the paradigm of matching the structure of a soil release polymer with the structure of the fabric, a method successful in the polyester soil release polymer field, has nevertheless yielded marginal results when applied to cotton fabric soil release agents. The use of methylcellulose, a cotton polysaccharide with modified oligomeric units, proved to be more effective on polyesters than on cotton.
For example, U.K. 1,314,897, published Apr. 26, 1973 teaches a hydroxypropyl methyl cellulose material for the prevention of wet-soil redeposition and improving stain release on laundered fabric. While this material appears to be somewhat effective on polyester and blended fabrics, the disclosure indicates these materials to be unsatisfactory at producing the desired results on cotton fabric.
Other attempts to produce a soil release agent for cotton fabric have usually taken the form of permanently modifying the chemical structure of the cotton fibers themselves by reacting a substrate with the polysaccharide polymer backbone. For example, U.S. Pat. No. 3,897,026 issued to Kearney, discloses cellulosic textile materials having improved soil release and stain resistance properties obtained by reaction of an ethylene-maleic anhydride co-polymer with the hydroxyl moieties of the cotton polymers. One perceived drawback of this method is the desirable hydrophilic properties of the cotton fabric are substantially modified by this process.
Non-permanent soil release treatments or finishes have also been previously attempted. U.S. Pat. No. 3,912,681 issued to Dickson teaches a composition for applying a non-permanent soil release finish comprising a polycarboxylate polymer to a cotton fabric. However, this material must be applied at a pH less than 3, a process neither suitable for consumer use nor compatible with laundry detergents which typically have a pH greater than 8.5.
U.S. Pat. No. 3,948,838 issued to Hinton, et al describes high molecular weight (500,000 to 1,500,000) polyacrylic polymers for soil release. These materials are used preferably with other fabric treatments, for example, durable press textile reactants such as formaldehyde. This process is also not readily applicable for use by consumers in a typical washing machine.
U.S. Pat. No. 4,559,056 issued to Leigh, et al. discloses a process for treating cotton or synthetic fabrics with a composition comprising an organopolysiloxane elastomer, an organosiloxaneoxyalkylene copolymer crosslinking agent and a siloxane curing catalyst. Organosilicone oligomers are well known by those skilled in the art as suds suppressors.
U.S. Pat. No. 5,332,528 to Pan, et al. discloses detergent compositions containing one or more anionic primary surfactants and a soil release composition consisting of a soil release agent and an anionic surfactant interactive nonionic hydrophile and/or an anionic surfactant interactive hydrophobic moiety or both, together with a soil release agent enhancer consisting of a polyhydroxy fatty acid amide.
Other soil release agents not comprising terephthalate and mixtures of polyoxy ethylene/propylene are vinyl caprolactam resins as disclosed by Rupert, et alia in U.S. Pat. Nos. 4,579,681 and 4,614,519. These disclosed vinyl caprolactam materials have their effectiveness limited to polyester fabrics, blends of cotton and polyester, and cotton fabrics rendered hydrophobic by finishing agents.
U.S. Pat. No. 6,242,404 to Dahanayake, et al. discloses a soil release polymer composition comprising a soil release polymer and a long chain nonionic alkoxylate surfactant and/or amphoteric that is able to generate very low critical micelle concentration values in water. Preferably, the soil release composition is incorporated in a detergent system such as a commercial laundry detergent which comprises a second anionic, nonionic or cationic surfactant and mixtures thereof. By lowering the cmc values of the detergent wash water to very low levels, the surfactant greatly enhances the performance of the soil release polymer.
In addition to the above cited art, the following disclose various soil release polymers or modified polyamines; U.S. Pat. No. 4,548,744, Connor, issued Oct. 22, 1985; U.S. Pat. No. 4,597,898, Vander Meer, issued Jul. 1, 1986; U.S. Pat. No. 4,877,896, Maldonado, et al., issued Oct. 31, 1989; U.S. Pat. No. 4,891,160, Vander Meer, issued Jan. 2, 1990; U.S. Pat. No. 4,976,879, Maldonado, et al., issued Dec. 11, 1990; U.S. Pat. No. 5,415,807, Gosselink, issued May 16, 1995; U.S. Pat. No. 4,235,735, Marco, et al., issued Nov. 25, 1980; WO 95/32272, published Nov. 30, 1995; U.K. Patent 1,537,288, published Dec. 29, 1978; U.K. Patent 1,498,520, published Jan. 18, 1978; German Patent DE 28 29 022, issued Jan. 10, 1980; Japanese Kokai JP 06313271, published Apr. 27, 1994; WO/1997/042288, published Nov. 13, 1997.
Many different approaches can be used to change the surface energy (hydrophilicity/hydrophobicity) and thus the adhesion properties of a given material. For example chemical treatments like plasma or ozone for polyethylene and polypropylene surfaces to increase hydrophilicity. Or physico-chemical treatments like the adhesion of surfactant molecules onto hydrophobic surfaces can alter them hydrophilic. Also the adhesion of polymers onto surfaces is used to change surface properties. One specific example would be the adsorption of polyethylene oxide (PEG). In all cases specific chemical groups are attached to the initial surface. These chemical groups change the surface energy and thus the adhesion properties and/or other surface properties like tendency of fouling or slip.
Two of the main disadvantages of the above mentioned treatments are poor durability and/or they are expensive/technically sophisticated. One example of the former is surfactants. They get easily washed away from the surface upon rinsing with e.g. water. An example for the latter is plasma or ozone treatment. Further, for some applications no satisfying solution is found up to date. One example would be improved anti-soil properties for cotton.
Materials that have a low surface energy, such as, for example, polyolefin polymers, have hydrophobic surfaces. The hydrophobic properties of such materials are not desirable in some applications and methods for hydrophilizing low surface energy substrates, including treatment with surfactants and/or high energy treatment, are known. Each of these methods has significant limitations. Surfactant treatments tend to wash off when a treated substrate is exposed to water and the charges imparted to the surface of a treated substrate by high energy treatment tend, particularly in the case of a thermoplastic polymer substrate, to dissipate. The hydrophilic properties of such surfactant treated substrates and high energy treated substrates thus tend to exhibit limited durability. Furthermore, the surfactants that are rinsed off of a treated substrate by exposure to water alter the properties of the water, such as lowering the surface tension, which may also be undesirable.
It would be advantageous to provide a laundry detergent composition which imparts improved anti-deposition and/or anti-adhesion properties to fabric being cleaned, particularly anti-soil deposition and anti-soil adhesion properties.